Inorg. Chem. 1983, 22, 2466-2468
2466
temperature, a result of depopulating the higher energy well; this is consistent with the experimental results and strongly implies that the cis-octahedral C u N 4 0 2 chromophore is fluxional. The fact that the 6’ values of 1 are greater than those of 2, a dl0 complex whose crystal is isostructural, indicates that the “driving force” governing the distortional behavior is vibronic in origin and is not related to crystalpacking forces etc. (Cooperative forces in 1 are also unimportant: the electronic reflectance and ESR spectra for Cu(11)-doped 2 show no discernible variations from 0.1-100% copper d ~ p i n g . ~The ) derivation presented allows AE to be easily determined from X-ray diffraction experiments performed at different temperatures, and it seemingly repudiates the notion that “X-ray analysis thus provides information about the preferred conformations of molecules although it has nothing to say about the energy differences between the conformations or the energy barriers that separate them. This information has to be obtained by other methods.”23 Acknowledgment. This work was supported by the National Science Foundation (Grant No. CHE-81-14613). We also wish to thank the Molecular Structure Corp. College Station, TX, for their help in obtaining the room and liquid-nitrogen data sets and for the use of their computing facilities and Richard E. Marsh, California Institute of Technology, for his very useful comments. Registry No. 1, 23578-78-1. Supplementary Material Available: Tables of final positional and thermal parameters (Tables S 1 and S2), bond distances and angles (Tables S 3 and S4), and observed and calculated structure factors (Tables S5 and S6) (32 pages). Ordering information is given on any current masthead page. (23) Dunitz, J. D. ‘X-ray Analysis and the Structure of Organic Molecules”; Cornell University Press: Ithaca, NY, 1979; p 312.
Contribution from the Institute for Inorganic Chemistry, University of Gottingen, Gottingen, West Germany, and the Department of Chemistry, Manchester University, Manchester M13 9PL, U.K.
Steric and Crystal-Packing Effects on the Molecular Structures of Dimetal(I1) Tetrakis(2-oxypyridine) Complexes William Clegg,*la C. David Garner,*Ib Lalarukah Akhter,lb and M . Hassan Al-Sammanlb Received November 2, 1982
The anions of 6-methyl-2-hydroxypyridine (Hmhp) and 6-chloro-2-hydroxypyridine(Hchp) form bridged binuclear complexes of the type M , ( m h ~ ) , ~and - ~ M2(~hp)46,7 with a number of transition metals. Across the series [Mo2(mh~)41.CH2C12,~ [R~A~~P)~I.C andH [Rh2(mhp)41,4 ~C~~,~ crystal structure determinations have demonstrated a pro~
~~
(a) University of Gottingen. (b) University of Manchester. (2) Cotton, F. A.; Fanwick, P. E.; Niswander, R. H; Sekutowski, J. C. J . (1)
Am. Chem. Soc. 1978, 100, 4725. (3) (a) Berry, M.; Garner, C. D.; Hillier, I. H.; MacDowell, A. A,; Clegg, W. Inorg. Chim. Acta 1981, 53,L61. (b) Clegg, W. Acta Crystallogr., Sect. E 1980, 836, 3112. (4) (a) Berry, M.; Garner, C. D.; Hillier, I. H.; MacDowell, A. A,; Clegg, W. J . Chem. SOC.,Chem. Commun. 1980, 494. (b) Clegg, W. Acta Crystallogr., Sect. B 1980, 836, 2437. ( 5 ) Clegg, W.; Garner, C. D.; AI-Samman, M. H. Inorg. Chem. 1982, 21,
1897. (6) Cotton, F. A.; Ilsley, W. H.; Kaim, W. Inorg. Chem. 1980, 19, 1453. (7) Cotton, F. A,; Felthouse, T. R. Inorg. Chem. 1981, 20, 584.
0020-1669/83/1322-2466$01.50/0
Table I. Crystal DataQ
3
2
1
formula
C,,H,,N,O,Mo,
cryst color and habit fw cryst size, mm space group
yellow laths
C,,H,,N,O,Mo,~ C,,H,,N,O,Rh,~ CH OH CH,CI, orange blocks yellow biocks
624.4 0.35 X0.23 X 0.15 pi 8.865 (1) 10.724 (1) 13.750 (1) 85.69 (1) 77.98 (1) 77.36 (1) 1246.9 1.663
656.4 0.25 X0.12 X -0.19 P1 8.938 (1) 11.043 (2) 13.903 (2) 94.30 (2) 95.98 (2) 103.87 (2) 1317.9 1.654
723.2 0.19 X0.35 0.50 p 2 , In 12.705 (1) 17.240 (1) 12.769 (1) 90 103.58 (1) 90 2718.7 1.767
2 10.17 b
2 9.69 0.746-0.81 9‘
4 14.31 0.526-0.6 13‘
55 6101
55 6500
3591
5447
337
346
0.0005 0.063 0.060 2.26 1.13 0.81
0.0005 0.046 0.062 1.73 1.82 0.96
a, .A
b, A c, .A 01, d g P , deg 7,de!
v,a
dcalcd, g cm-3 Z M, cm-’
transmissn factor 28,,,, deg 50 no. of data 4597 collcd no. of data 2686 F > 40(F) no. of 319 refined parameters 0.0003 gd Re 0.028 0.039 R variance: e 0.98 slopeh 1.34 largest 0.35 peak,’ e A-3 f
x
a Valid for all three data sets: Stoe-Siemens AED diffractometer, Mo Ka radiation, h = 0.71069 A, graphite monochromator; all measurements at room temperature. No absorption corrections. Semiempirical absorption corrections based o n intensities measured at various azimuthal angles. Weighting scheme: w“ = d(F)+ g F z . e R =
‘
ZIAl/ZIFoI;A= IFol-IFcI.f R w = ( Z ~ A z / ~ ~ F o Z ) ” Z . Variance = ( Z w A ’ / Z w ) ” ’ . Slope of normal probability
plot.
In final difference synthesis.
gression toward longer M-M and shorter M-0 and M-N bonds. [Pd2(mhp)4]5differs markedly from the Rh dimer only in the M-M separation and angles that depend directly on it. In parallel with this progression is an increase in the mean 0-M-M-N torsion angle away from an exactly eclipsed conformation, in the order Mo < Ru < Rh = Pd. We have interpreted this as a direct consequence of intramolecular steric repulsions between methyl groups of the ligand^.^,^ We were, therefore, surprised to see a report of the structure of [Rh2( m h ~ ) , l . H ~ Oin, ~which two crystallographically independent molecules have mean torsion angles of 1.0 and 9.3’, which are respectively lower and higher than any previously observed for M2(mhp), complexes. Furthermore, the mean Rh-Rh bond length of 2.367 (1) 8, was interpreted as significantly longer than the 2.359 (1) 8,observed in anhydrous Rh2(mhp),., This structure raises the question of the effect of crystal-packing forces (the ultimate appeal of crystallographers in search of explanations!) on the molecular structures and, in particular, on the M-M bond lengths and torsional distortions about the M-M bonds in these dimers. In the course of our studies of complexes of mhp, we have obtained crystals of two further forms of Mo2(mhp),, one as a methanol solvate and the other with no solvent of crystallization. We report here the structures of these and of [Rh2(mhp),l.CHzClz. 0 1983 American Chemical Society
Notes
Inorganic Chemistry, Vol. 22, No. 17, 1983 2467
Table 11. Atomic Coordinates ( X lo4)
2
1
atom
3
X
Y
z
X
Y
3904 (1) 3042 (1) 1606 (3) 1555 (5) 563 (6) 560 (6) 1549 (7) 2482 (6) 3510 (7) 2514 (4) 5862 (3) 6079 (5) 7345 (5) 7495 (6) 6369 (6) 5159 (5) 3908 (6) 4977 (4) 4229 (3) 5058 (5) 5789 (6) 6670 (6) 6868 (6) 6148 (6) 6312 (7) 5216 (4) 2113 (4) 1056 (5) -116 (6) -1170 (7) -1080 (6) 61 (6) 242 (7) 1125 (4)
1787 (1) 3129 (1) 3912 (2) 2905 (4) 2954 (4) 1873 (5) 708 (5) 690 (4) -503 (4) 1777 (3) 1965 (2) 3103 (4) 3278 (4) 4477 (5) 5528 (5) 5329 (4) 6404 (4) 4124 (3) 3896 (3) 2871 (4) 2899 (5) 1815 (5) 672 (5) 654 (4) -506 (5) 1751 (3) 1227 (3) 2097 (5) 1766 (6) 2715 (6) 3990 (6) 4278 (5) 5617 (5) 3353 (4)
2802 (1) 2643 (1) 4051 (2) 4632 (3) 5574 (3) 6149 (4) 5810 (3) 4876 (3) 4434 (4) 4292 (2) 3341 (2) 3477 (3) 3857 (3) 4009 (3) 3787 (4) 3396 (3) 3129 (4) 3236 (2) 1185 (2) 738 (3) -272 (3) -701 (4) -139 (4) 845 (3) 1509 (4) 1279 (3) 2295 (2) 1972 (3) 1559 (4) 1193 (4) 1225 (4) 1644 (3) 1714 (4) 2026 (2)
3582 (1) 3818 (1) 5340 (6) 5820 (8) 6950 (9) 7430 (9) 6804 (10) 5698 (9) 4918 (12) 5202 (7) 5443 (6) 6195 (9) 7415 (10) 8132 (10) 7694 (9) 6535 (9) 6021 (10) 5790 (7) 2459 (6) 1889 (8) 1064 (10) 448 (11) 605 (10) 1404 (9) 1604 (11) 2079 (7) 1667 (6) 1106 (8) -185 (9) -716 (9) 33 (9) 1278 (9) 2173 (11) 1839 (7) 3754 (12) 4714 (24)
1297 (1) 1792 (1) 3551 (5) 3851 (7) 4965 (8) 5254 (8) 4442 (8) 3362 (8) 2444 (9) 3063 (6) 470 (5) 425 (7) -189 (8) -238 (9) 333 (8) 952 (8) 1600 (9) 971 (6) 109 (5) -779 (8) -1963 (8) -2860 (9) -2591 (8) -1416 (8) -1020 (9) -517 (6) 2022 (5) 2537 (7) 3038 (7) 3575 (8) 3635 (8) 3148 (8) 3141 (10) 2595 (6) 4656 (10) 3735 (14)
Z
Y
Z
1742 (1) 498 i i j 867 (1) 1583 (2) 1835 (2) 2593 (3) 3114 (3) 2866 (2) 3382 (3) 2099 (2) 1445 (2) 742 (2) 537 (3) -208 (3) -756 (3) -537 (2) -1088 (3) 197 (2) 109 (2) 552 (2) 236 (3) 686 (3) 1452 (3) 1739 (3) 2559 (3) 1292 (2) 2059 (2) 1588 (2) 1824 (3) 1334 (3) 606 (3) 383 (2) -408 (2) 873 (2)
2729 (1) 3311 i i j 4861 (2) 5087 (3) 6168 (3) 6412 (4) 5595 (4) 4554 (4) 3615 (4) 4307 (3) 2971 (2) 3241 (3) 3344 (4) 3660 (4) 3842 (4) 3737 (3) 3925 (4) 3438 (2) 1788 (2) 1015 (3) -46 (3) -833 (4) -639 (4) 378 (4) 658 (4) 1203 (3) 2478 (2) 2715 (3) 2576 (4) 2857 (4) 3272 (4) 3381 (3) 3744 (4) 3125 (2)
1222 (9) 2181 (2) 533 (1)
9823 (7) 9408 (2) 8918 (2)
X
3523 (1) 2130 (1) 2575 (3) 3499 (5) 3835 (6) 4809 (6) 5448 (6) 5114 (6) 5755 (6) 4142 (4) 3612 (3) 2863 (5) 2861 (7) 2042 (7) 1239 (7) 1265 (5) 449 (6) 2075 (4) 1423 (4) 1932 (5) 1510 (7) 2066 (7) 3072 (7) 3495 (6) 4560 (6) 2923 (4) 3679 (4) 2965 (5) 3002 (6) 2233 (7) 1391 (7) 1364 (6) 514 (6) 2138 (5) 8669 (6)
1779 (1) 2463 (1) 2820 (2) 2679 (3) 2975 (3) 2857 (5) 2425 (5) 2137 (4) 1672 (5) 2269 (3) 318 (2) 134 (3) -897 (3) -1103 (4) -261 (4) 741 (3) 1675 (4) 938 (2) 2108 (2) 1584 (4) 1261 (4) 685 (5) 415 (5) 762 (4) 562 (5) 1339 (3) 3234 (2) 4040 (3) 5075 (4) 5928 (4) 5798 (4) 4800 (3) 4584 (4) 3943 (2) 3793 (11) 4118 (2) 3868 (3)
Table 111. Structural Features of M,(mhp),.L and M,(chp), Complexes
M, (mhp), .L
M Mo
Mo
Mo
Ru
Rh
Rh
Rh
Pd
Rh
W
Cr ~~~~
L M-M, A meand(M-N), A mean d(M-O), A meand(M-N) mean d(M-0), A mean N-M-M-O torsion, deg ref
CH,C1, 2.065 (1) 2.167 (14) 2.086 (7) 0.081 (16)
2.067 2.171 2.077 0.094
1.3 (4)
1.4 (9)
(1) (7) (4) (9)
MeOH 2.068 (1) 2.174 (10) 2.081 (9) 0.093 (12)
CH,CI, 2.238 (1) 2.359 2.089 (5) 2.043 2.044 (10) 2.017 0.045 (12) 0.026
0.8 (6)
3.5 (6)
6.1 (9)
3
4
2
(1) (5) (4) (5)
~
CH,Cl, 2.367 (1) 2.053 (5) 2.019 (9) 0.034 (10)
H,O 2.370 2.045 2.021 0.024
3.7 (5)
1.0 (8)
9.3 (6)
6.4 (12)
1.9 (3)
1.4 (8)
7
7
5
2
2
(1) (8) (6) (9)
H,O 2.365 2.037 2.017 0.020
(1) 2.546 (8) 2.046 (5) 2.013 (9) 0.033
CH,Cl, (1) 1.889 (1) (16) 2.067 (4) (8) 1.969 (9) (18) 0.098 (10)
CH,C1, 2.161 (1) 2.11 (3) 2.037 (7) 0.07 (3)
M,(chu),
M M-M, A mean d(M-N), A meand(M-01, A
M
Cr
W
Mo
Rh
1.955 (2) 2.060 (10) 1.978 (11)
2.177 (1) 2.12 (3) 2.07 (1)
2.085 (1) 2.153 (11) 2.089 (9)
2.379 (1) 2.050 (19) 2.011 (12)
Experimental Section Mo2(mhp), (1) was as crystals directly from the reaction of Hmhp with M~(co), in diglyme (18 h at "r temperature under purified dinitrogen), analogous to the original preparation of W2(mhp)4.2 Recrystallization of this from methanol gave crystals of [Mo,(mhp),].MeOH (2). [Rh2(mhp),].CH2C12 (3) was obtained by recrystallization of Rh2(mhp)44from CH2CI2.' Crystals of each complex were sealed
meand(M-N) mean d(M-0), A meanN-M-M-0 torsion, deg ref
Cr
W
Mo
Rh
0.082 (13)
0.05 (4)
0.064 (13)
0.039 (24)
4.3 (12)
3.0 (13)
3.1 (10)
4.8 (12)
6
6
6
I
in Lindemann glass capillaries for X-ray investigation. The methods used for data collection and structure determination have been described el~ewhere.~ All three structures were refined with anisotropic thermal parameters and with hydrogen atom constraints.* Crystal (8) Computer programs were written by G. M. Sheldrick (SHELXTL system; Gottingen) and W. Clegg (diffractometer control program) for Data General Eclipse and Nova computers.
2468
Inorg. Chem. 1983, 22, 2468-2470
Figure 1. Molecular structure of Rh,(mhp), in 3. Thermal motion is shown as 50% probability ellipsoids.
data are summarized in Table I. Atomic coordinates are given in Table 11. Table I11 compares the essential results with those of previously determined M,(mhp), and M,(chp), structures. Detailed results, together with structure factor tables, are available as supplementary material. Results and Discussion The molecular structure of 3 is depicted in Figure 1; the atom-numbering scheme is the same as in all our studies of Mz(mhp), structures. The structure is essentially the same as for 1, 2, and the other related dimers. The molecular structure of Moz(mhp)4 varies insignificantly with crystal packing in all three crystal structures; no significant differences are observed in the bond lengths or even in the conformational twist about the Mo-Mo bond. It might be expected that the eclipsed conformation of a quadruple bond, which contains a 6 component, would be particularly insensitive to factors favoring a twisting distortion, but torsion angles of up to 30' have been observed, whereby the 6 component has been estimated to lose only approximately 50% of its contribution to the Mo-Mo b ~ n d i n g . ~ The single Rh-Rh bond shows a greater variation of twist, reflecting its inherently weaker nature and the u symmetry of the net Rh-Rh bond. The range of observed Rh-Rh bond lengths in these Rh2(mhp), structures is, however, very small, and the differences observed are of dubious significance in the absence of special precautions in the determination of unit cell parameters. When all the crystallographic results now available for molecules of this type are considered together, it appears that the torsional conformation of the MZ(mhp), and M,(chp), molecules is determined by a balance of several factors, which are given as follows, in decreasing order of importance. (1) Bonding Characteristics of the M2 Unit Bridged by Four Ligands of the mhp Type. The preference here is always for an eclipsed conformation, with that for the Mo-Mo quadruple bond being significantly more marked than that for the Rh-Rh single bond. (2) Intramolecular Steric Interactions between the Ligands, Notably the M e M e or Cl...Cl Interactions of Mutually Trans Ligands. A twist away from the eclipsed conformation relieves this repulsion. We have already discussed this effect for M2(mhp), c ~ m p l e x e sand ~ * ~note that the known M2(chp), structures also fit into this pattern (Table 111). These Mz(chp), complexes (and Rh,(mhp),) are all isostructural (space group Pbca), so variations in packing forces are slight. The relatively small increase in mean torsion angle in moving from Mo,(chp), to RhZ(chp),, compared with the rather larger difference for the corresponding mhp complexes, mirrors the smaller varia(9) Cotton, F. A.; Fanwick, P. E.; Fitch, J. W.; Glicksman, H. D.; Walton, R. A. J. Am. Chem. SOC.1979, 101, 1752.
0020-166918311322-2468$01 .SO10
tion in [mean d(M-N) - mean d(M-0)] for the chp complexes; Le., the intramolecular steric repulsion effect shows much less variation for the chp complexes. Moreover, in both groups of complexes Mz(mhp), and M,(chp), with M = Cr, Mo, or W,z,6the largest degree of twisting distortion is for M = Cr; here steric interaction will be at its greatest for each triad, because of the shorter Cr-N bonds. Although these torsion angles, and differences between them, are small, a satisfactory and convincing overall pattern does emerge from the complete set of known structures. Extreme steric effects, with twists of around 20°, are observed when four mhp or chp ligands are arranged about a Rh2 unit, such that three methyl groups or chlorine atoms lie at one end of the m o l e ~ u l e . ~ ~ ' ~ (3) Intermolecular Interactions between Molecules and with Solvent Molecules. For normal van der Waals interactions (when the solvent of crystallization is methanol, CH2C12,or nonexistent), the effect is a minor one, overlaid on factors 1 and 2. In the case of [Rhz(mhp),].HzO, however, the rather stronger hydrogen bonds7 have a much greater effect on the torsional conformation of the dimeric molecule. Acknowledgment. We thank the SERC and the Verband der Chemischen Industrie for financial support. Registry No. 1, 67634-80-4; 2, 86257-95-6; 3, 86177-69-7. Supplementary Material Available: Listings of bond lengths and angles, thermal parameters, atomic coordinates, and structure factors (80 pages). Ordering information is given on any current masthead page. (10) (a) Berry, M.; Garner, C. D.; Hillier, I. H.; Clegg, W. Inorg. Chim. Acra 1980, 45, L209. (b) Berry, M.; Garner, C. D.; Clegg, W., to be sub-
mitted for publication.
Contribution from the Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 X-ray Diffraction and Thermal Analysis of Molybdenum(VI) Oxide Hemihydrate: Monoclinic MoOj"/2H201 R. L. Fellows,*2M. H. Lloyd,* J. F. Knight,3 and H. L. Yakel, Received June 15, 1982
Molybdenum(V1) oxide is known to form a rich family of crystalline hydrates that include a monoclinic dihydrate, M 0 0 ~ . 2 H ~ 0two , ~ monohydrates, the yellow monoclinic Mo03.H206and the white triclinic Mo03-H20,7and a white hemihydrate.8 A molybdenum oxide hemihydrate phase has (1) Research sponsored by the Division of Chemical Sciences, Office of
Basic Energy Sciences, U S . Department of Energy, under Contract W-7405-eng-26 with the Union Carbide Corp. (2) Chemical Technology Division. (3) Current address: Oak Ridge Gaseous Diffusion Plant, Separations Systems Division. (4) Metals and Ceramics Division. ( 5 ) Krebs, B. Chem. Commun. 1970, 50. ( 6 ) Gunter, J. R. J. Solid Stare Chem. 1972, 5, 354. (7) Boschen, I.; Krebs, B. Acta Crystallogr., Sect. B 1974, B30, 1795. Oswald, H. R.; Giinter, J. R.; Dubler, E. J. Solid Stare Chem. 1975, 13, 330. See also: Powder Diffraction File, JCPDS International Center for Diffraction Data, Swarthmore, PA; No. 26-1449. (8) Vorob'ev, S. P.; Davydov, I. P. Russ. J. Inorg. Chem. (Engl. Transl.) 1966, 11, 1087; Zh. Neorg. Khim. 1966, 9, 2031.
0 1983 American Chemical Society
